U.S. patent number 4,617,485 [Application Number 06/682,851] was granted by the patent office on 1986-10-14 for rotor of alternator mounted on vehicle.
This patent grant is currently assigned to Nippondenso Co., Ltd.. Invention is credited to Toshiaki Hotta, Shigenobu Nakamura, Takayasu Nimura.
United States Patent |
4,617,485 |
Nakamura , et al. |
October 14, 1986 |
Rotor of alternator mounted on vehicle
Abstract
An improved construction of Randel-type rotor of a
vehicle-mounted alternator, capable of reducing the windage noise
which is produced as a result of interference between the rotor and
the stator of the alternator. The rotor has a pair of pole cores
provided with a plurality of mutually meshing claws, and an
exciting coil disposed at the inner side of the pole cores. Spacers
in the form of an integral ring or discrete wedges are fitted in
the spaces between adjacent pole core claws so as to provide a
substantially smooth cylindrical outer peripheral surface of the
rotor portion facing the radial teeth on the stator.
Inventors: |
Nakamura; Shigenobu (Chiryu,
JP), Nimura; Takayasu (Nagoya, JP), Hotta;
Toshiaki (Oobu, JP) |
Assignee: |
Nippondenso Co., Ltd. (Kariya,
JP)
|
Family
ID: |
26334055 |
Appl.
No.: |
06/682,851 |
Filed: |
December 18, 1984 |
Foreign Application Priority Data
|
|
|
|
|
Dec 19, 1983 [JP] |
|
|
58-237871 |
Jan 6, 1984 [JP] |
|
|
59-946 |
|
Current U.S.
Class: |
310/65; 310/214;
310/263; 310/59 |
Current CPC
Class: |
H02K
1/243 (20130101); H02K 1/325 (20130101); H02K
3/528 (20130101) |
Current International
Class: |
H02K
1/22 (20060101); H02K 1/24 (20060101); H02K
1/32 (20060101); H02K 3/46 (20060101); H02K
3/52 (20060101); H02K 001/32 () |
Field of
Search: |
;310/263,52,257,51,62,63,43,45,156,214,61,58,59,85,86 ;417/423R,368
;415/143 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Skudy; R.
Attorney, Agent or Firm: Cushman, Darby & Cushman
Claims
What is claimed is:
1. In a vehicle-mounted alternator having a rotor including a pair
of Randel-type pole cores having mutually meshing claws and an
exciting coil provided at the inner side of said pole cores, and a
stator having teeth extending radially inwardly to oppose said
rotor,
an improved rotor construction comprising: spacers made of a
non-magnetic material and disposed between adjacent pole core claws
of said pole cores in such a manner as to provide, together with
said claws, a substantially smooth cylindrical outer peripheral
surface for a portion of said rotor facing said teeth of said
stator which prevents the flow of air radially between said claws
of said portion and also provide a space constituting a passage for
cooling air axially between the inner sides of said spacers and the
outer peripheral surface of said exciting coil.
2. A rotor construction according to claim 1, wherein outer
peripheries of gaps between the meshing claws are smaller than
inner peripheries and said spacers comprise wedges press-fitted
into said gaps.
3. A rotor construction according to claim 1, wherein said spacers
are constituted by hollow tubular members.
4. A rotor construction according to claim 1, wherein flanges for
retaining said spacers are formed on the circumferential ends of
the outer peripheral surface of each of said pole core claws.
5. A rotor construction according to claim 1, wherein a plurality
of said spacers are formed integrally to form of a ring having
convexities and concavities in its outer peripheral surface.
6. A rotor construction according to claim 5, wherein said ring is
contacted by side surfaces and inner peripheral surfaces of said
claws of said pole cores.
7. A rotor construction according to claim 6, wherein said ring is
shaped integrally from a plastic and is held with a tightening
margin between inner peripheral surfaces of said claws and the
outer peripheral surface of said exciting coil.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rotor of an alternator for use
on vehicles and, more particularly, to an alternator rotor provided
with a Randel-type pole core having a plurality of meshing
claws.
2. Description of the Prior Art
Japanese Patent Laid-Open No. 79455/1983 discloses an example of
the construction of rotor of a vehicle mounted alternator, improved
to provide a greater cooling effect. In this alternator rotor, a
pair of rotor cores, each having pole cores in the form of a
plurality of axially projecting claws, are fixed to the rotor shaft
such that exciting coils fixed to a yoke are clamped between the
pair of rotor cores. The pole core arrangement in which the pole
cores of a pair of rotor cores oppose and mesh each other is
generally referred to as "Randel-type Pole Core". The invention
disclosed in the above-mentioned Japanese patent Laid-Open No.
79455/1983 is intended for reducing the air flow resistance to
increase the flow rate of the cooling air, and the alternator
disclosed therein meets this requirement.
SUMMARY OF THE INVENTION
It is a current trend to reduce the size and weight while
increasing the power of vehicle-mounted alternators. To this end,
it is attempted to drive the alternator at higher speeds than ever,
by increasing the pulley ratio. This in turn causes, however, an
increase in the windage noise generated in the alternator. Namely,
when the rotor having the Randel-type pole cores rotates at a high
speed, the side surfaces of the pole core claws cause centrifugal
windage effect in the areas between the pole core claws so that a
pulsating air pressure is produced in the area between the stator
and the pole cores. This pulsating pressure interferes with the
concavities and convexities in the teeth portion on the inner
periphery of the stator, thus producing the above-mentioned windage
noise.
Accordingly, it is a primary object of the invention to provide a
rotor for vehicle-mounted alternator, improved to eliminate the
windage noise caused by the aerodynamic interference between the
pole cores and the stator, without impairing the flow of the
cooling air within the rotor.
To this end, the invention provides, in a vehicle-mounted
alternator having a rotor constituted by a pair of pole cores
having alternately meshing claws and exciting coils wound on the
inner side of the pole cores, and a stator having teeth radially
opposing the rotor, an improvement of the rotor which comprises:
spacers, for example, an integral ring made of a non-magnetic
material or separate wedges constituted by resin pipes, fitting in
the spaces formed between adjacent claws of pole core such that at
least the portion of the rotor opposing to said teeth exhibits a
smooth cylindrical outer peripheral surface.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic illustration of the whole construction of an
alternator to which the invention is applied;
FIG. 2 is a schematic illustration showing a part of the
arrangement of the stator and the rotor of the alternator shown in
FIG. 1;
FIG. 3 is a perspective view of a ring member mounted between the
pole cores of a first embodiment in accordance with the
invention;
FIG. 4 is a perspective view of a rotor on which the ring member
shown in FIG. 3 is mounted;
FIG. 5 is a sectional view taken along the line V--V of FIG. 4;
FIG. 6 is a side elevational view of a portion of the ring member
used in the first embodiment;
FIG. 7 is a sectional view taken along the line VII--VII of FIG.
6;
FIG. 8 is a sectional view taken along the line VIII--VIII of FIG.
7;
FIG. 9 is an illustration of a portion of an alternator, showing
the arrangement of the stator and the core thereof in accordance
with a second embodiment of the invention;
FIG. 10 is a perspective view of an essential part of an alternator
rotor to which the second embodiment of the invention is
applied;
FIG. 11 is a vertical sectional schematic illustration of an
essential part taken along the line XI--XI of FIG. 10;
FIGS. 12 to 15 are vertical sectional views of essential parts of
another embodiment of the invention;
FIG. 14A is a perspective view of a pole core wedge; and
FIG. 14B is a vertical sectional schematic illustration of an
essential part having the pole core wedges attached thereto.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Preferred embodiments of the invention will be described
hereinunder with reference to the accompanying drawings. FIG. 1 is
an illustration of the construction of an alternator to which the
invention is applied, while FIG. 2 shows a portion of the
alternator to illustrate the arrangement of the stator and pole
core in the alternator. The alternator has a shell constituted by a
pair of frames 9,9' each having a bowl-like form. The frames 9,9'
are jointed together at their open end surfaces and are fixed to
each other by a plurality of stud bolts 10 and cooperating nuts 8
(only one stud bolt and one nut are shown). A stator 2 is fixed to
the inner peripheral surface of the frame 9 by means of said stud
bolts 10. The stator 2 is composed of a stator core 2-a and a
stator coil 2-b wound on the stator core 2-a. As well known to
those skilled in the art, the stator core 2-a has a plurality of
pole teeth (referred to simply as "pole teeth", hereinunder) on the
inner peripheral surface thereof. Tubular bearing boxes 19,19' are
formed on the central portions of side surfaces of both frames 9,9'
so as to project therefrom inwardly of the alternator. These
bearing boxes 19,19' hold bearings 11,11' which carry a shaft 4
rotatably. A pair of claw-type pole cores 1,1' are mechanically
fixed to the shaft 4 so as to be housed by the stator. The pole
cores 1,1' clamp therebetween a rotor coil 5 which is known per se.
Centrifugal fans 7,7' having a diameter smaller than the inside
diameter of the stator are fixed by suitable means to the outer
sides of the pole cores 1,1' such that the vanes 7-a,7-a' of the
fans 7,7' project axially away from the pole cores 1,1'. The fan 7
is of the slant-flow type having vanes 7-a inclined forwardly as
viewed in the direction of rotation so that it forcibly supplies
the cooling air into the pole cores 1,1'.
On the opposing surfaces of the pair of end frames 9,9' are formed
shrouds 9-a,9-a' opposing the vanes 7-a,7-a' of the fans 7,7'
across a small gap so as to serve as guide vanes for the fans 7,7'.
Suction windows 9-b,9-b' are formed in the portions of the both end
frames 9,9' adjacent to the bearings 11,11' on the both end frames
9,9' so that cooling air is induced by the fans 7,7' through these
suction windows 9-b,9-b'. Discharge windows 9-c,9-c' for outgoing
heated air are formed in the portions of the end frames 9,9'
confronting the outer periphery of the stator coil 2-b. (The
discharge window 9-c' is omitted from the drawings.)
A pulley 12 disposed outside the end frame is coupled by a nut 13
to the end of the shaft 4 projected to the outside of the bearing
11. The pulley 12 and, hence, the shaft 4 is adapted to be driven
by an engine (not shown). Electric parts such as a diode fin 14
having a diode (not shown), a brush holder 15 having brushes 15-a
for supplying the rotor coil with exciting current, and an IC
regulator (not shown) for regulating the output voltage are fixed
to the outer side of the frame 9' and is covered by a rear cover
16. The rear cover 16 is formed in such a manner as to surround the
diode fin 14, brush holder 15 and the regulator, and is provided in
its side wall with holes through which cooling air is supplied to
cool the regulator and the diode fin. In FIG. 2, a symbol R
represents the direction of rotation of the rotor.
An explanation will be made hereinunder as to an embodiment of the
alternator rotor of the invention. Referring to FIG. 2, in order to
avoid any leakage of magnetic flux between the pole claws and to
ensure an effective application of the magnetic flux to the stator
2, the claws 1-p,1-p' of the pole cores 1,1' of the rotor have
inside widths m',n' smaller than the outside widths m,n both at the
base and extreme ends thereof.
In the rotor in accordance with the invention, a plastic ring or
spacer 3 is mounted to fill the gaps between adjacent claws
1-p,1-p' of the pole cores 1,1' and the gaps between back surfaces
1-b of the claws (see FIG. 2) and the rotor coil 5, in a manner as
shown in FIGS. 4 and 5. The plastic ring 3 has a configuration as
shown in FIGS. 3 and 6. Namely, the plastic ring 3 has a continuous
ring-like form constituted by a claw-back plate 3-b and claw-side
plates 3-a which are shaped to embrace the back surface 1-b and
both side surfaces 1-a of each claw 1-p, and curved outer
peripheral plate 3-c which fills the outer peripheral space between
opposing claws 1-p,1-p'. Ribs 3-d are extended radially inwardly
from the claw-back plate 3-b towards the center of the rotor coil
5. As will be seen from FIG. 6, ribs 3-d are disposed at 30.degree.
interval. The plastic ring 3 is fixed axially between the side
surfaces 1-c,1-c' (side surface 1-c' not shown) of base ends of the
pair of pole cores 1,1' and the end surfaces 3-f,3-f' of the
claw-back plates 3-b, while the ribs 3-d are fixed to the radially
outer end of the rotor coil 5 and the back surface 1-b of the pole
core mechanically in such a manner as to leave a certain tightening
margin. The axial width of the resin ring 3 should be, at the
smallest, such that the convexities and concavities in the outer
periphery of the pole core claws 1-p,1-p' opposing the teeth 2-a of
the stator 2 are eliminated when the ring 3 is mounted between the
pole cores 1,1'. Ring or spacer 3 also prevents flow of air
radially between the claws 1-p1-p'. The plastic ring or spacer 3 is
so shaped as to form spaces 3-e between the inner sides and the
outer peripheral plates 3-c and the rotor coil 5 that is axially of
the rotor. The air induced by the centrifugal fans 7-a,7-a' flows
through these spaces 3-e i.e. axial of the rotor.
Another embodiment of the invention will be described hereinunder.
FIG. 10 is a perspective view of an essential part of another
embodiment of the alternator rotor in accordance with the
invention, while FIG. 11 is a schematic vertical sectional view
taken along the line XI--XI of FIG. 10. As will be seen from these
Figures, this embodiment employs pipe-shaped pole core wedges 23
press-fitted in the spaces formed between the opposing side
surfaces 1-a,1-a' of adjacent claws 1-p,1-p' of the pole cores
1,1'. Each pole core wedge 23 has an axial length which is, at the
smallest, large enough to eliminate any convexities and concavities
on the portion of the outer periphery of the pole core claws
confronting the stator teeth 2-a. The pole wedge cores thus
mechanically fitted in the gaps between the side surfaces of the
claws are subjected to an impregnation treatment for enhancing the
insulating power. This impregnation treatment enhances also the
strength of fixing of the pole core wedges 23.
In order to further improve the resistance of the pole core wedges
against the centrifugal force, flanges 1-b' as shown in FIG. 12 may
be formed on the circumferential ends of each pole core claw.
The pole core wedge 23 can have a substantially U-shaped form as
shown in FIG. 13. This pole core wedge may be used in combination
with the pole core having the flanges 1-b'.
The pole core wedge need not have a continuous peripheral surface.
Namely, it can have a tubular form provided with an
axially-extending key-way 23a formed therein, as shown in FIGS. 14A
and 14B so that it can be compressed and driven into the gap
easily.
Although in the described embodiment the pole core wedge 23 is made
from a resin, the pole core wedge can be made from other materials.
For instance, it can be made from a non-magnetic metal such as
aluminum, stainless steel or the like, by die-casting, press or
cold forging. The pole core wedge need not always be hollow but may
be solid.
FIG. 15 shows a modification in which the pole core wedge 23 is
provided in its side walls with slots which receive collars 1-c'
projected circumferentially from both side surfaces of the pole
core claw.
The operation of the vehicle-mounted alternator itself is well
known and, therefore, will be explained only briefly. Exciting
current is supplied to the rotor coil 5 through brushes 15-a and
slip ring. At the same time, the pulley 12 is driven by the engine
to rotate the rotor coil 5, so that an alternating voltage E is
induced in the stator coil 2-b. The output voltage is rectified by
a rectifier and is regulated by the regulator, as is well
known.
The alternator rotor of the invention produces the following
effect.
When the shaft 5 rotates, the cooling fans 7-a, 7-a' on both sides
of the pole cores 1,1' are rotated to induce ambient air of low
temperature through the suction windows 9-b,9-b'. The air first
cools the bearings 11,11' and then cools the stator coil 2-b. The
heated air is discharged through the discharge window 9-c. A part
of the cooling air is forced to flow towards the pole cores 1,1' so
as to absorb heat from the rotor coil 5 and to cool the stator coil
2-b before it leaves the alternator through the discharge window
9-c.
When a part of the cooling air passes the area around the pole
cores 1,1', particularly in the current high-speed alternator, the
side surfaces 1-a of the pole core claws 1-p act as fan blades to
produce centrigugal flow of air to cause a pulsation of air
pressure in the area between the stator 2 and the pole cores 1,1',
thus generating unfavourable windage noise due to interference
between the opposing convexities and concavities of the stator
teeth 2-a and the slots. This problem, however, can be overcome by
the invention. Namely, in the alternator having the rotor in
accordance with the invention, the spaces between the side surfaces
of adjacent pole core claws are filled by the plastic ring 3 which
provides a smooth cylindrical outer peripheral surface of the pole
core claws 1-p,1-p' having no substantial convexities and
concavities, so that the side surfaces 1-a of the pole core claws
does not produce centrifugal fan effect, so that the generation of
the windage noise due to the centrifuged air and the convexities
and concavities presented by the stator teeth 2-a is avoided.
In addition, the claw-back plates 3-b of the plastic ring 3 covers
the back surfaces 1-b of the pole cores to provide a surficient
insulation between the outer peripheral surface of the pole core
and the inner peripheral surface of the pole core claws 1, so that
the rotor coil 5 can be formed at a sufficiently large space
factor. The plastic ring 3 can be stably and securely held because
it is fitted with tightening margin between two pole cores 1,1' and
between the back surface 1-b of the pole claws and the rotor coil
5. In addition, since the claw-back plates 3-b abutting the back
surfaces 1-b of the pole core claws are formed integrally with the
curved outer peripheral plates 3-c, the undesirably breaking and
separation of the curved outer peripheral plates 3-c due to
centrifugal force is avoided advantageously.
Since spaces 3-e are formed at the inner side of the outer
peripheral plates 3-c of the ring 3, the cooling air induced by the
cooling fans 7 during rotation of the rotor coil 5 is allowed to
flow axially as in the case of the conventional alternator rotor
despite the presence of the plastic ring 3, so that the rotor coil
5 can be cooled sufficiently.
In the conventional alternator rotor, a part of the cooling air is
forced to flow towards the stator 2 by the centrifugal fan effect
produced by the claws 1-p,1-p' so as to impair the effect of
cooling of the rotor coil 5. In contrast, in the stator rotor of
the invention, the whole part of the air can flow through the
passage between the pole core claws 1-p,1-p' so that the rotor coil
5 can be cooled effectively.
Although in the described embodiment the ring 3 is made of a
plastic, this is not exclusive and the ring 3 may be shaped from a
non-magnetic material such as aluminum, stainless steel or the like
by a press, cold forging or the like, followed by a coating with an
electrically insulating paint.
In the illustrated embodiments, the ribs 3-d for pressing the pole
core claws 1-p,1-p' has a split form consisting of two radially
inward projections. The rib 3-d, however, can be composed of a
single projection or three or more projections. The ring 3 itself
may be composed of a plurality of separate segments, although in
the described embodiment it is an integral member.
In the second embodiment of the invention, the pole core wedges 23
fitted in the spaces between the pole core claws provide
substantially smooth cylindrical outer peripheral surface of the
rotor portion opposing to the teeth 2-a of the stator, as in the
case of the first embodiment. Therefore, the side surfaces of the
pole core claws 1-a do not produce any centrifugal fan effect so
that the generation of unfavourable windage noise is avoided even
in the high-speed operation of the alternator. Since the axial
spaces or passages are left between the pole core wedges 23 and the
outer peripheral surface of the coil 5, the air can flow axially as
in the case of the conventional alternator core, so that the
cooling of the coil 5 is never impaired. Rather, the cooling effect
is enhanced because the provision of the pole core wedges 23
ensures the passage of the whole part of the cooling air through
the gaps between the pole core claws, unlike the conventional
alternator core in which a part of the air is scattered towards the
stator to impair the effect of cooling of the rotor coil 5.
As has been described, according to the invention, the rotor of the
invention for vehicle-mounted alternator has a non-magnetic ring or
pole core wedges fitted in the gaps between the adjacent claws of
the pole cores in such a manner as to provide a substantially
smooth cylindrical outer peripheral surface of the rotor portion
facing the teeth on the stator. Therefore, the unfavourable windage
noise, which is inevitable in the conventional alternator due to
interference between the pole core and the stator teeth, is avoided
to reduce the level of noise during high speed rotation of the
rotor. In addition, since the ring and the pole core wedges are
constructed to allow the air from the cooling fans to flow into the
spaces between the pole cores, the heat generated by the rotor coil
in the rotor can be effectively carried away by the cooling
air.
* * * * *